The long-term goal of this research is to understand how extracellular signals trigger cells to differentiate into a polarized, motile state. Whereas cellular motility is required for normal biological processes such as morphogenesis and wound healing, motility also contributes to cancer metastasis. Therefore it is important that the acquisition of motility be tightly regulated. The differentiation of C. elegans sperm provides a model system for studying this regulation. Like other migratory cells, these sperm move by crawling, and their maturation - termed sperm activation -- involves a transformation from a symmetrical, immotile spermatid to a highly polarized, motile spermatozoon capable of directional motility. While genetic studies have shown that sperm activation is subject to controls that differ between males and hermaphrodites, and a variety of compounds have been identified that can activate sperm in vitro, no in vivo activation trigger has been identified. This proposal is designed to test the hypothesis that one such trigger may involve proteolysis. Our preliminary studies have identified a protease inhibitor, SWM-1, and serine protease, TRY-5, that appear to function antagonistically to regulate sperm activation in males. To extend these observations, our specific aims are to (1) determine in which contexts try-5 function is required for sperm activation and how its activity is coordinated among different tissues; (2) determine whether SWM-1/TRY-5 can function as a protease-inhibitor system to regulate sperm activation in in vitro assays, and test candidate targets for try-5-dependent cleavage in vivo; and (3) identify additional factors that promote sperm activation downstream of swm-1. These studies will provide insight into two widely important biological phenomena: the regulation of cellular motility and protease-mediated signaling. Furthermore, since proteases are important therapeutic targets for cancer and other diseases, this work may be applicable to the development of novel inhibitors. PUBLIC HEALTH RELEVANCE: The acquisition of a polarized, migratory cellular morphology is crucial for the normal processes of development and wound healing, and also contributes to the abnormal transition to metastasis in cancer cells. C. elegans sperm differentiation provides a model system for studying the signals that trigger the transition of cells to a migratory morphology. We are using C. elegans to study one such signal that is mediated by proteases, an important family of enzymes that is present in all animals and in humans.